Marking element for mechanical pencils



N; H. M PHEE MARKING ELEMENT FOR MECHANICAL PENGILS Jan. 13, 1942.

Original Filed Jan. 13 1937 Fz'y. 1. Fly. 2. Fig.3.

INVENTOR.

TTORNEY Patented Jan. 13, 1942 MARKIN G ELEMENT FOR MECHANICAL PENCILS Nathaniel H. MePhee, New Rochelle, N. Y.

Original application January 13, 1937, Serial No. 120,346. Divided and this application April 6, 1939, Serial No. 266,268

'7 Claims.

My invention relates to improvements in mechanical pencils and more particularly to those used for drafting purposes, and the same has for its object to provide a simple, eificient and inexpensive marking element or lead for mechanical pencils which does not require sharpening or pointing to produce uniform lines of predetermined thinness.

Further, said invention has for its object the provision of a marking element or lead in which the thickness at its marking end will remain constant without regard to the angular position in which the pencil is usually or normally held in drawing a line.

Further, said invention has for its object the provision of a marking element or lead by means of which a succession of lines of predetermined thinness may be made Without necessitating any sharpening thereof.

Further, said invention has for its object the provision of a flat marking element or lead for mechanical pencils which is of such thinness as to require external support, andwhose transverse thickness will remain constant at the marking end throughout the entire length of the element as the same wears away in the course of use regardless of the angle at which the pencil is held in use.

Further, said invention has for its object the provision of a marking element or lead for mechanical pencils and drawing instruments which element is of such extreme thinness that the cross-sectional dimension or thickness at its marking end will remain constant throughout the length of the element as the same wears away in use, and which is of such flexibility to require external support throughout its entire length to render the same usable for its intended purposes.

Other objects will in part be obvious and in part be pointed out hereinafter.

To the attainment of the aforesaid objects and ends my invention consists in the novel features of construction, and in the combination, connection and arrangement of parts hereinafter more fully described and then pointed out in the claims.

In the accompanying drawing Fig. 1 is a detail face view, greatly exaggerated, showing a single marking element or lead constructed according to, and embodying my said invention;

Fig. 2 is an edge view thereof;

Fig. 3 is an enlarged side view of a mechanical pencil employing a marking element or leadembodying my said invention;

Fig. 4 is a longitudinal section of the pencil on the line 4-4 of Fig. 5;

Fig. 5 is a transverse section on the line 5-5 of Fig. 4;

Fig. 6 is a similar section on the line 6-6 of Fig. 4, and

Figs. 7 and 8 are respectively enlarged detail face and edge views of the Working end or tip of the pencil.

In said drawing I have shown one form of mechanical pencil l0 which is designed to receive a marking element ll formed of graphite, crayon or other suitable material embodying my invention, and in said drawing the pencil is shown comprising a tubular member or barrel l2 having a central opening extending entirely through the same in which is secured a tubular, metal, actuating-member l3, provided upon its inner surface with screw-threads I3 Within said threaded member i3 is disposed a holding or guiding member I l having a passage l5 extending longitudinally thereof, which passage is of rectangular form in cross-section and corresponds to that of the marking element or lead disposed therein. The holder I4 is formed of two opposing, registering, flexible metallic sections or halves HI having registering longitudinal grooves l6, and elongated recesses l1 cooperating to form a longitudinal slot communicating with the passage l5 formed by said two grooves It. The walls of the slot formed by the recesses I! are preferably tapered, as indicated at l8, to facilitate the introduction of the marking element or lead ll edgewise into the holder I4, and to provide space for the follower lugs. The lower or working end [9 of the holder I4 is of reduced cross-section and is enclosed by the sleeve 20 for holding said sections together at the lower end thereof. The upper end of the holder is secured together by a knurled head or member 2!, which also serves as the actuator for rotating the holder within the tubular member or barrel l2. The two sections or halves I l are preferably resilient or flexible, and upon removal of the sleeve 20 the unsecured ends thereof will flare or diverge outwardly.

When said sections are secured together by the sleeve 20 and head 2i they tend to expand, bow or spread apart between the points of securement thereby enlarging the passage I5 and facilitating the insertion of the marking element or lead II, and the cleaning of the pencil. The two sections are beveled at the lower end of the slot 15, as indicated at 22, for directing the marking element I I into the tip 23 of the holder. The portion of the passage 1 5 within the tip 23 is preferably of less width than the thickness of the lead H so that the Working end of the lead tends to expand or spread the opposing portions N of the sections M and thereby maintain the lead firmly gripped or clamped frictionally at the working or marking end thereof. In order to allow for the slight separation of the portions M clearance is provided between the holder [4 and the sleeve 20.

The working end or tip 23 of the holder 14 comprises opposite flat surfaces 26 paralleling the plane or the wide dimension of the passage l5, and serving as guiding surfaces engageable with a straight edge, T-square or triangle when a line is to be drawn. The lower edge of the holder [4 is preferably rounded or beveled at to obviate sharp points or corners which would otherwise be liable to cut or tear the paper, and the lower or discharge end 21 of the passage I5 is preferably flared to prevent the shearing or breaking oif of the working end of the lead.

The holder I4 is adapted to receive a leadadvancing member or follower 23, corresponding in cross-section to that of the lead II and the passage IS. The follower 28, when inserted in the passage l5, yieldingly engages the walls of said passage frictionally to prevent the follower from slipping into the entrance slot H. The follower 28 includes the two lateral projections or lugs 29 which extend through the slot l1, and

are in threaded engagement with the screwthreads 3 on the inner surface of the tubular member 13 with which the same cooperate to advance or retract the follower when the holder i4 is rotated by the head 2 I. member I4 is rotated relative to threaded member l3 the follower 28 will be advanced to feed the lead or marking element H. The casing or barrel [2 also serves to compress the sections M to bring the same together in close fitting relation about the marking element H and follower 28 in order to retain the same in alignment and prevent displacement thereof within the slot [5. When it is desired to insert a lead or marking element the holder M may be readily withdrawn g,

from the barrel l2, and the marking element then inserted edgewise through the expanded passage l5. Upon replacement within the barrel l2 the sections M are slightly compressed to reinforce and confine the lead substantially throughout the entire length thereof, the frictional gripping action on the lead being greater at the lower or working end 23 of the holder.

In use the broad side of the lead or marking element is parallel with the direction in which the line to be drawn extends, and the strain on the lead is in the plane of the wide dimension thereof, this dimension being of an order to resist said strain. The width of the line to be drawn is primarily determined by the thickness of the lead, and inasmuch as this thickness is a minimum, very fine lines may be drawn, and the successive lines will all be of uniform width as the lead wears down. It therefore becomes unnecessary to sharpen or sand-paper the lead in order 3 to maintain a working point or edge of uniform thickness thereon.

The marking element or lead ii may be composed of graphite, crayon or other marking material, and is made in the form of a flat strip or elongated body of any convenient or desired length, approximately .035 of an inch wide, and of a thinness ranging from approximately .005 of an inch for the finer line to approximately .015 of an inch for the heavier line. The element is,

When the holding therefore, so light, thin and flexible that the same is incapable of use unless externally supported throughout its entire length by suitable holding means as in a pencil. Further, the element is of such thinness that when the pencil is held with the broad side of the element parallel with the direction in which the line is drawn, a line of minimum thickness will be produced which will be uniform and unchanging in width from beginning to the end of the element as the same wears away.

It is to be noted also that in drawing lines with the aid of a straight edge, such as a T-square, triangle or ruler, it is customary to hold the pencil or ruling pen in a vertical position, or one approximating the vertical. With applicants pencil, due to the extreme thinness of the marking element, the transverse thickness thereof at its marking or exposed end will not become appreciably greater as the element wears away no matter at what angle the pencil may be held relative to the plane of the broad side of the element in the normal course of drawing a line with the aid of a straight edge of any kind. The angular position of the pencil, except in extreme instances, will not be less than approximately forty-five degrees (45") to the horizontal, and within such range there can be no appreciable increase in the thickness or transverse dimension of the exposed or marking end of an element possessing the characteristics and thinness of applicants marking element.

When using the pencil, and guiding the same along the edge of a ruler, T-square or triangle in the same manner that a ruling pen is used by a draftsrnan it becomes possible to draw successively any number of lines of uniform width until the entire element or lead is completely consumed or worn away. And when the marking element is used in the holder of a compass or device for drawing circular lines, lines ranging from minimum to maximum may be produced by simply rotating the pencil or holder within the compass through an arc of ninety degrees the finest or thinnest line being then produced when the broad side of the element is disposed parallel to the general direction in which the line extends, and the maximum or broadest line when the element is adjusted upon the compass to a position at right angles to the general direction of the line to be drawn.

In this application no claim is made to the construction of the pencil, as the same constitutes the subject-matter of my copending application, filed January 13, 1937, Serial No. 120,346, now Patent No. 2,175,210, issued Oct. 10, 1939, of which this application is a division.

Having thus described my said invention, What I claim and desire to secure by Letters Patent is:

1. As a new article of manufacture, an eversharp marking element for mechanical pencils comprising a flat, elongated body having a thin dimension not exceeding .015 of an inch in thickness in which the percentage variation in the thin dimension at the marking end of the element is negligible, and in which said thin dimen sion remains substantially constant as the element wears away in the course of normal use of the pencil thereby insuring the production of fine lines of unvarying thickness when the pencil is held at diiferent inclinations from the vertical in a line of direction extending transversely to the broad side of the element.

2. As a new article of manufacture, an eversharp marking element for mechanical pencils comprising a flat, elongated body of graphite having a thin dimension not exceeding .015 of an inch in thickness and correspondingly highly frangible in which the percentage variation in the thin dimension at the marking end of the element is negligible, and in which said thin dimension remains substantially constant as the element wears away in the course of normal use of the pencil thereby insuring the production of a succession of fine lines of unvarying thickness when the pencil is held at different inclinations from the vertical in a line of direction extending transversely to the broad side of the element.

3. As a new article of manufacture, an eversharp marking element for mechanical pencils comprising a flat, flexible, elongated body of graphite having a thin dimension ranging from .005 to .015 of an inch in thickness in which the percentage variation in the thin dimension at the marking end of the element is negligible, and in which said thin dimension remains substantially constant as the element wears away in the course of normal use of the pencil thereby insuring the production of a succession of fine lines of unvarying thickness when the pencil is held at difierent inclinations from the vertical in a line of direction extending transversely to the broad side of the element.

4. As a new article of manufacture, an eversharp marking element for mechanical pencils comprising a fiat, elongated body of graphite having a thin dimension not exceeding .015 of an inch in thickness and in which the percentage variation in the thin dimension at its marking end is negligible, and in which said thin dimension remains substantially unchanging as the element wears away in the course of normal use of the pencil thereby insuring the production of a succession of fine lines of unvarying thickness as the angular position of the pencil from the vertical is varied in a line of direction extending transversely to the broad side of the element.

5. As a new article of manufacture, a marking element for mechanical pencils comprising a flat, elongated body of graphite of a thinness not exceeding .015 of an inch and in which the percentage variation in the thin dimension at its marking end is negligible and remains substantially unchanging thereby insuring the production of a succession of fine lines of uniform thickness, regardless of the angular position of the pencil from the vertical in a line of direction extending transversely to the broad side of the element as said element wears away in the course of the normal use of the pencil.

6. A fiat, thin, elongated lead for mechanical pencils not exceeding approximately .015 inch in thickness so that the percentage variation of the area at the marking end thereof, when the pencil is held in an angular position, is negligible and which is not less than approximately .005 inch and capable of being handled without breaking while being inserted into the pencil;

- said lead being somewhat flexible and requiring to be laterally confined throughout the length thereof for use.

7. As a new article of manufacture a marking element for mechanical pencils comprising a flat, elongated body of graphite of a thinness varying from .005 to .015 of an inch between which limits the percentage Variation in the thin dimension thereof is negligible and remains substantially unchanging thereby insuring the production of a succession of fine lines of uniform thickness, regardless of the angular position of the pencil from the vertical in a line of direction extending transversely to the broad side of the element, as the element wears away in the course of the normal use of the pencil.

NATHANIEL H. MCPHEE. 

